Flotation frother



Patented July 22, 1941 UNITED STATES FLOTATION FROTHER Ludwig J.Christmann, Bronxville, and David W. Jayne, Jn, Port Chester, N. Y.,assignors to American Cyanamid 00., New York, N. Y., a

corporation of Maine No Drawing.

Application November Serial No. 172,898

3 Claims. (01. 209-166) This invention relates to frothers and more moreparticularly, to frothers for the froth flotation of ores.

Cresylic acids have been used with many ores as frothers in frothflotation and may be considered as standard. They are available in twoboiling ranges, the lower boiling range consisting of cresols and somexvlenols and the higher mainly xylenols with a few higher. homologs. Inspite of the fact that cresylic acids have been standard frothers forthe most various types of froth flotation for so many years, they arenot ideal and many synthetic frothers have been proposed, among whichsome, such as mixtures of aliphatic alcohols of 7-10 carbon atoms withsaturated hydrocarbons as described in our Patent #2,065,053 have goneinto extensive use. These synthetic frothers despite their greaterefliciency are expensive and have not been successful in displacingcresylic acids for all purposes because of the relatively low price ofcresylic acids until recently and their availability all over the world.

We have found that thereason why cresylic acids are not as effectivefrothers as could be desired lies in the fact that the length of theside chains on the phenol nucleus is too short. We have found thatremarkable increases in frothing efficiencies are obtained when higheralkyl homologs or derivatives of phenol are used as frothers. Theimprovement is quite marked by substituting an ethyl for a methyl groupand even better results are obtained with still longer alkyl chains suchas propyl and butyl. Good results are obtained with longer side chainsbut decreasing solubilities set a limit. It is also possible to usealicyclic derivatives such as terpinyl phenols. We have found that themethyl group is not disadvantageous but it is not suificiently long byitself, therefore, while the invention includes higher allwlated phenolswhich are free from methyl groups, we prefer to alkylatecresols as theraw material is somewhat cheaper and the presence of the methyl groupadds somewhat to the efficiency of the resulting higher alkylatedcompounds as frothers.

The increase in frothing efficiency between methyl phenols and ethylphenols is quite marked and rises rapidly to the propyl and butylphenols such as isopropyl and secondary or tertiary butyl. Still longerhydrocarbon chains such as amyl or hexyl give good froths but theincrease in eiiiciency over the isopropyl and butyl derivatives is toosmall to warrant the added price. Therefore, for practical reasons, weprefer to use the propyl or butyl derivatives such as isopropyl andtertiary or secondary butyl derivatives and these constitute thepreferred embodiment of the invention. I

The present invention is not concerned with any particular method ofalkylation but we have found that with the higher alcohols such aspropyl and butyl and especially the secondary and tertiary alcohols, thealkylation proceeds smoothly and simply by heating with -80% sulfuricacid as a condensing agent. Any other method of alkylation may, ofcourse, be used.

A typical alkylation is as follows:

A mixture of 1 mol of cresylic acid (boiling range, 200-215 C.) and 1mol of isopropyl alcohol are heated at 70-75 C. with an excess of 70%sulfuric acid the heating being maintained for three hours with goodagitation. After an additional half hour of agitation, the batch iscooled and the oil layer which contains the propylated cresylic acid isseparated from the aqueous phase, drawn off, washed with water, thenwith 10% soda ash solution, dried over anhydrous sodium sulfate andfiltered. The product is a clear dark red oil having a density of 0.98at C. as compared with 1.022 for the original cresylic acid. The weightyield is about of the theory and the distillation range is approximately210-250 C.

It is not necessary to alkylate to the point where an of the phenols arealkylated and the invention includes frothers in which some of thephenols or cresols are not alkylated.

The efficiency of the frothers was tested on a lead ore having thefollowing analysis: a

Per cent Pb 8.37 Fe 3.10 Insoluble 10.22 S 1.86

The ore was ground to 48 mesh and transferred to a Fagergren flotationmachine. A lead promoter was added and one portion of the ore wastreated with propylated cresylic acid and the other with theunpropylated product. The concentrates were collected, filtered, dried,weighed and assayed. In the tests, the only variable was the nature ofthe frother and all other conditions including amount of. frother weremaintained Tertiary butylated cresylic acids when tested on the same oregave recoveries practically the same as the propylated'cresylic acidsbut with a slightly higher grade. It will be apparent that;

I the alleviated cresols are markedly superior to the unalkylatedcresylic acid, especially from the standpoint of recovery which isimproved by 10%. The exact amount by which recoveries are improved bythe use of the frothers of the present invention will vary withdifierent ores but in all which we have tested, marked improvements areobtained by using the alkylated cresylic acids.

Terpinyl phenols gave substantially similar results to the propylatedcresols but their higher cost renders themcommercially less attractivealthough they are not excluded from the present invention.

What we claim is:

1. A method of froth flotation of lead ores which comprises subjecting apulp of lead ore to froth flotation in the presence of a flotationpromoter and a frother containing a major proportion of alkylated crudelow boiling cresylic acid mixture, said alkyl radical being from two tofive carbon atoms in length.

2. A method of froth flotation of lead ores which comprises subjecting apulp of the material to be floated to froth flotation in the presence ofa flotation promoter and a frother containing a major proportion of'propylated crude low boiling cresylic acid mixture.

3. A method of froth flotation of lead ores which comprises subjecting apulp of the material to be floated to froth flotation in the presence ofa flotation promoter and a frother containing a major proportion ofbutylated crude low boiling .cresylic acid mixture.

LUD WIG J. CHRISTMANN. DAVID W. JAYNE, JR.

